Failing heart valves can become calcified and stenotic. Valvuloplasty is a procedure that can break calcification and open up heart valves. With the advent of percutaneous transcatheter heart valve replacement (“PTVR”), the importance of valvuloplasty devices and procedures may increase, since a valvuloplasty procedure may be required to facilitate the proper placement and/or expansion of a percutaneously delivered valve. Use of valvuloplasty in connection with PTVR is expected to present unique challenges not previously addressed or accounted for by the valvuloplasty prior art.
One problem associated with prior art balloon-based valvuloplasty devices is that the balloon may conform to the profile of the stenosed native valve, as opposed to forcing the stenosed valve to conform to a desired predetermined shape or profile of the balloon. Furthermore, some balloon-based valvuloplasty devices completely occlude the native valve and thereby stop the flow of blood during the valvuloplasty procedure. This severely limits the amount of time over which the procedure may be practiced and brings additional risks to the already debilitated patient, thereby limiting the patient population on whom the procedure may be performed.
Pedersen US 2005/0090846 is a balloon-based device that incorporates a valve within the balloon in order to maintain blood flow during the valvuloplasty procedure. In such a device, the balloon may require a relatively large cross-sectional area in order to generate the substantial radial pressure against the native valve necessary to perform the procedure, thereby increasing its profile and reducing the patient population in which the device may be utilized. As such, a balloon-based valvuloplasty device that incorporates a valve may only partially overcome the problem of flow occlusion during valvuloplasty, since its use may be limited by size constraints.
Another problem associated with prior art balloon-based valvuloplasty devices is the tendency of the valvuloplasty balloon to slip out of the stenotic area during the valvuloplasty procedure. Such slippage may, for example, arise as a result of the pressures exerted on the device by blood ejected from the beating heart, or as a function of how the valvuloplasty device inflates. A number of device designs have been conceived to try to reduce or eliminate slippage. Some of these designs make use of a shaped balloon in which a necked-in region is intended to interface with the stenosed region of the native valve (see, for example, PCT Publication No. WO 99/15223 to Cardeon Corporation, published Apr. 1, 1999). However, use of a valvuloplasty device incorporating a necked-in region requires precise placement of the valvuloplasty balloon prior to inflation and may not adequately dilate the target region. Other designs make use of an “ordered inflation”, wherein the balloon sequentially inflates, for example, with the distal end of the balloon beginning to inflate first, followed by inflation of the proximal end and final inflation of the center of the balloon positioned across the native valve. See, e.g., Owens et al. U.S. Pat. No. 4,986,830.
An alternative prior art valvuloplasty technique, described, for example, in U.S. Pat. No. 6,932,838 to Schwartz et al., utilizes a number of “ribs” which, when constrained in such a way as to decrease the distance between their proximal and distal ends, “bulge” radially outward and apply radially outward-directed forces to the stenotic native valve. These devices suffer from a number of shortcomings. The minimal number of point contacts associated with the small number of ribs is expected to localize forces, thereby increasing the risk of localized tissue failure, e.g., perforation or dissection. Such devices also may be less efficient at transmitting the force provided by the medical practitioner into the radially- and outwardly-directed forces necessary for expansion of the native stenosed valve, as compared to traditional balloon valvuloplasty devices. Furthermore, these devices may require precise placement both axially and rotationally relative to the stenotic native valve.
In view of the drawbacks associated with previously known methods and apparatus for performing valvuloplasty, it would be desirable to provide methods and apparatus that overcome those drawbacks. It also would be desirable to provide methods and apparatus for performing valvuloplasty that address the unique challenges associated with using such methods and apparatus as adjuncts to percutaneous transcatheter heart valve replacement.